1. Field of the Invention
The present invention relates to an image pickup apparatus capable of inputting an image of substantially high image quality by finely varying the optical angle of a parallel-plane plate glass or a reflecting mirror which is provided in the optical path of an image pickup system.
2. Description of Related Art
In recent years, image input apparatuses such as video cameras and scanners have made remarkable advances, and far higher image quality and far higher resolution have been strongly demanded. However, to increase the number of pixels per image pickup element involves a number of problems, such as performance problems such as a lowering in sensitivity or S/N, an increase in cost due to a decrease in production yield, and the necessity for an expensive quartz-crystal low-pass filter or the like for preventing a false signal or the like.
What is called xe2x80x9cpixel shiftingxe2x80x9d is known as a method of increasing the image quality and the resolution of an image pickup apparatus without increasing the number of pixels per image pickup element. The pixel shifting is a method of finely vibrating an image pickup element itself or sequentially obtaining optical-video information by conducting, to photosensitive portions on the image pickup element, optical-image information which would have reached non-photosensitive portions between adjacent photosensitive portions, while varying the reflection angle of a reflecting mirror disposed in an optical path in an optical relay space between a lens unit and the image pickup element or while varying the incident angle of light on an optical transmission glass having the shape of a parallel-plane plate or varying the thickness of the optical transmission glass by using the refraction of light by the optical transmission glass which is disposed in such optical path. According to such pixel shifting, it is possible to obtain an image having a high resolution which is substantially equivalent to a resolution obtainable when the number of pixels of an image pickup element is increased.
Since this method makes it possible to pick up an image of high image quality without increasing the number of pixels of the image pickup element itself, the pixel shifting is a method which is extremely effective in increasing the resolution of the image input apparatus.
Specific examples of pixel shifting using the above-described principles have been disclosed. For example, Japanese Laid-Open Patent Application No. Sho 59-15378 discloses the art of rotating a parallel-plane plate about an axis parallel to a pixel array, Japanese Laid-Open Patent Application No. Hei 1-121816 discloses the art of inclining a parallel-plane plate surface and rotating it about an optical axis, and Japanese Laid-Open Utility Model Application No. Hei 6-8937 discloses the art of driving a cam mechanism by means of a motor and varying the inclination of a parallel-plane plate surface in the directions of X and Y axes.
However, in any of the above-described conventional mechanism examples which use a parallel-plane plate optical-transmission glass, a motor is used as a drive source which varies the optical position of the parallel-plane plate optical-transmission glass and a complicated expensive mechanism such as a position control mechanism using a cam is used, with the result that it is difficult to ensure the positioning accuracy of the parallel-plane plate optical-transmission glass and it is also difficult to increase the driving speed thereof.
If two horizontal and vertical systems each including a motor, a cam and a mechanism for transmitting the drive force of the motor are incorporated in an image pickup apparatus, a number of problems will occur; for example, the entire pixel shifting mechanism necessarily becomes larger in size and difficult to dispose in the space between the lens unit and the image pickup element.
To cope with the above-described problems, the assignee of the present invention has filed Japanese Patent Application No. Hei 9-4476 dated Jan. 14, 1997 as an image pickup apparatus and an optical apparatus each of which includes a pixel shifting system intended to solve the problems and capable of being driven at high speed by means of a simple arrangement.
The present invention is intended to solve the above-described problems and to realize a further increase in driving speed of the invention of Japanese Patent Application No. Hei 9-4476.
A first object of the present invention is to provide an optical apparatus and an image pickup apparatus both of which are capable of performing extremely high-speed pixel shifting.
A second object of the present invention is to provide an optical apparatus and an image pickup apparatus both of which have a small-size and high-speed pixel shifting function which is easy to control.
A third object of the present invention is to provide an optical apparatus and an image pickup apparatus both of which are capable of performing high-speed pixel shifting in either direction.
To achieve the above objects, in accordance with one aspect of the present invention, there is provided an image pickup apparatus which comprises image pickup means for photoelectrically converting an optical image formed on an image pickup surface and outputting a picked-up image signal, an optical element for shifting an incident position of incident light on the image pickup surface, a plurality of restricting portions for controlling an inclination position of the optical element with respect to an optical axis by engaging with the optical element, and driving means for driving the optical element to engage the optical element with the plurality of restricting portions, wherein the driving means includes electromagnetic driving means, and permanent magnets are respectively disposed in portions of the optical element which are to be exposed to an action of electromagnetic force of the electromagnetic driving means, the optical element being driven by an electromagnetic circuit formed by the permanent magnets of the optical element and the electromagnetic driving means.
In accordance with another aspect of the present invention, there is provided an optical apparatus which comprises an optical element for shifting an incident position of incident light on an image pickup surface, a plurality of restricting portions for controlling an inclination position of the optical element with respect to an optical axis by engaging with the optical element, and driving means for driving the optical element to engage the optical element with the plurality of restricting portions, wherein the driving means includes electromagnetic driving means, and permanent magnets are respectively disposed in portions of the optical element which are to be exposed to an action of electromagnetic force of the electromagnetic driving means, the optical element being driven by an electromagnetic circuit formed by the permanent magnets of the optical element and the electromagnetic driving means.
In accordance with another aspect of the present invention, there is provided a lens unit or a camera apparatus in which the aforesaid optical apparatus is integrally incorporated.
Other objects, features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. dr
FIGS. 1(a) and 1(b) are diagrammatic perspective views aiding in explaining the arrangement and the operation principle of a pixel shifting system according to a first embodiment of the present invention;
FIGS. 2(a), 2(b) and 2(c) are diagrammatic views aiding in explaining the arrangement and the operation principle of the pixel shifting system according to the first embodiment of the present invention;
FIGS. 3(a) and 3(b) are diagrammatic views aiding in explaining the arrangement and the operation principle of the pixel shifting system according to the first embodiment of the present invention;
FIG. 4 is a diagrammatic view aiding in explaining the vertical pixel shifting operation of the pixel shifting system according to the first embodiment of the present invention;
FIG. 5 is a diagrammatic view aiding in explaining the vertical pixel shifting operation of the pixel shifting system according to the first embodiment of the present invention;
FIG. 6 is a diagrammatic view aiding in explaining the vertical pixel shifting operation of the pixel shifting system according to the first embodiment of the present invention;
FIG. 7 is a diagrammatic view aiding in explaining the vertical pixel shifting operation of the pixel shifting system according to the first embodiment of the present invention;
FIG. 8 is a diagrammatic view aiding in explaining the horizontal pixel shifting operation of the pixel shifting system according to the first embodiment of the present invention;
FIG. 9 is a diagrammatic view aiding in explaining the horizontal pixel shifting operation of the pixel shifting system according to the first embodiment of the present invention;
FIG. 10 is a diagrammatic view aiding in explaining the horizontal pixel shifting operation of the pixel shifting system according to the first embodiment of the present invention;
FIG. 11 is a diagrammatic view aiding in explaining the horizontal pixel shifting operation of the pixel shifting system according to the first embodiment of the present invention;
FIG. 12 is a view aiding in explaining the pixel shifting operation of the pixel shifting system according to the first embodiment of the present invention;
FIGS. 13(a), 13(b) and 13(c) are diagrammatic views showing the arrangement of a second embodiment of the present invention;
FIG. 14 is an exploded perspective view showing an arrangement in which a pixel shifting system according to any of the embodiments of the present invention is incorporated as a unit;
FIG. 15 is a diagrammatic cross-sectional view showing an arrangement in which the unit of a pixel shifting mechanism according to any of the embodiments of the present invention is actually incorporated into a camera body;
FIG. 16 is a block diagram showing a circuit arrangement for picking up an image by using the pixel shifting system according to any of the embodiments of the present invention;
FIGS. 17(a) and 17(b) are views showing the principle of pixel shifting;
FIGS. 18(a) and 18(b) are views aiding in explaining the principle of a driving method for pixel shifting according to the present invention; and
FIGS. 19(a) and 19(b) are views aiding in explaining the way of increasing the speed of a driving operation for pixel shifting according to the present invention.